Prior art windings for an electric machine, whether they are of the stator or rotor type, are made from a plurality of turns of a conductive material, generally copper, formed by winding a lead wire around two or more polar expansions of the stator and/or the rotor of the electric machine. The winding, through which an electric current passes, must be suitably insulated from the polar expansions, which are made from ferromagnetic material. For this purpose, prior art places a layer of electrically insulating material between the winding and the corresponding polar expansion on which it is wound.
Electric currents, including high ones, pass through the winding and cause heating due to the Joule effect which extends through the entire winding and adjacent areas of the electric machine.
In particular, it has been found that the heat produced in this way deteriorates the conductivity properties of the lead wire, which consequently generates a greater resistance to the passage of current causing a high and often unacceptable energy loss.
In addition, the overheating of the winding may result in fast deterioration of the insulation characteristics of the above-mentioned layer of electrically insulating material placed between the winding, and the corresponding polar expansion on which it is wound. This results in evident risks of short circuits and permanent damage to the electric machine, which must therefore be replaced or undergo costly maintenance.
This situation is particularly serious in rotary electric machines of the sealed type, in which the windings are immersed in a sealed environment subjected to continuous heating due essentially to the above-mentioned heating caused by the Joule effect. This sealed environment is not subject to an exchange of air, and, under steady-state conditions, there may be high temperatures inside this environment which favour overheating of the windings.